Thanks, Rob, I updated the OP with the new link.
Re: left-click scrolling, I think a single-click works as well, but that's not the problem. I did not see a method to scroll to an item in the TreeBox, so I'm scrolling to a position I gather from the item at that index. It's possible that I'm using the wrong coordinates; I noticed similar behavior but most of the time it worked. I'll look into this.
Re: view-source, while I don't get the segfault on Linux, it can produce an unrecoverable state. I'm not exactly sure what causes this, but I hoped no one would try! I presume it's because I'm directly setting HTML content instead of pointing to a source file, yet it may have to do with my event handling. I'm hoping I can disable this right-click menu. Otherwise, it's a method to get up a creek without a paddle.